Photography



Patented July 17, 1928.

UNITED STATES PATENT OFFICE.

EASTMAN A. WEAVER, OF BROOKLINE, MASSACHUSETTS, ASSIGNOR, BY MESNE AS-SIGNMEN'IS, TO TECHNICOLOR MOTION PICTURE CORPORATION, OF BOSTON, MASSA-CHUSETTS, A CORPORATION OF MAINE.

PHOTOGRAPHY.

Application filed November 2, 1921. Serial No. 512,890.

This invention relates particularly to the production of relief picturesin gelatine or other suitable medium but it may also be utilized in theproduction of other kinds of 6 photographic pictures. It has beendeveloped for use in producing motion pictures in colors but it is alsoapplicable in producing black-and-white motion pictures or in producingstill pictures whether black-and- 10 white or colored. In the productionof color pictures the invention may be utilized either in an additiveprocess, eg in which the complemental images are separately projectedalong'a branched path into registry on a screen, or in a subtractiveprocess, e. g. in

which the complement-a1 images are superposed in registry and projectedalong a single optical path.

In many branches of the art of photography difiicultyhas' beenexperienced in securing the proper contrast throughout the high-light,half-tone and shadow regions respectively. In some cases the contrast isunsatisfactory only in the high-light regions or only in the shadowregions, but in few cases can satisfactory gradations (i. e. variationsin optical density relative to the variation of light intensitythroughout corresponding portions of the object field) be seecuredthroughout all three regions, especially in the various color processesemploying stained reliefs.

This difliculty is particularly pronounced in relief processes where themost striking detect in the appearance of the pictures is the exceisivedifference or contrast between light and intermediate values as comparedwith the difference between intermediate and dark values. This isaccompanied by an excessive degree of lost detail (which in ordinarysilver pictures is produced in mild degree by insuificient exposure);and ordinarily the lightest areas of the pictures have no detailwhatsoever, merely consisting of clear celluloid. \Vhen producingpositive reliefs by printing from negatives, for example, if theprinting is increased to record this highlight detail, the intermediatevalues become still more excessively dark; and if in turn this relievedby decreasing contrast, the deep shadows of the pictures become gray orbrown. In other Words, if the printing and contrast are such as toproduce satisfactory detail in the high-lights and good black shadows,half-tones such as faces arelayers will be longer than that for thinlayers, and as a commercial process requires the time of imbibition tobe reduced to a minimum the deepest densities suffer some-' what fromthis cause. Thirdly, owing to the non-uniform spectral absorption ofordinary dyes successive additions of equal quantities of dye produce acontinually decreasing series of effects on the color, since the portionof the spectrum most heavily absorbed by the dye will be largelyfiltered out by the earlier portions, so that the residual light is lesssubject to modification by the later strata. This corresponds to thewellknown phenomenon experienced in using two identical color filtersover a photographic lens, the second filter producing much less changein exposure than the first. Another process in which certain of theaforesaid causes also operate against proper contrast gradations is thatin which a plurality of stained complemental relief imageserehsuperposed and viewed with transmitted ig t.

A principal diificulty encountered in making photographic reproductionsby means of gelatine reliefs is the tendency toward straightness of thecharacteristic curve, commonly called the H & D curve. In the typicalcurve for silver images the lower portlon of the curve representing theunder exposure is concave upwardly, the intermediate pos tionrepresenting the average exposure is straight, and the upper portionrepresenting the over exposure is the relief curve the first and thirdportions tend to drop out, particularly when monochromatic light isemployed in the exposure or in case the absorbing power of theemulconvex upwardly. In

sion is substantially in rior processes has rendered the use of relieimages unsatisfactory.

Objects of the present invention are to correct "defects in the contrastgradations of photographic images, particularly relief images for use'incolor photography, to control the contrast gradations at will to producedesired photographic and artistic effects, to increase the concavity ofthe characteristic curve in the lower portion ordinarily referredto asthe under-exposure region, and to reduce the required image exposures inmaking relief pictures.

The present invention consists in exposing the film with lightdistributedv to produce an image, as for example by contact printing,and also with light adapted to alter the contrast gradations of thepicture or to reduce the required image exposure or both. For

convemence I shall refer to the first as the 7 image exposure and thesecond as the contrast exposure although the two exposures may beeffected simultaneously as a single exposure and the contrast exposuremay also be an image exposure as will hereinafter appear.

The contrast exposure may be made either before or after the ima eexposure as for example by running the through a printer having a lightof predetermined intensity and quality. When exposed to the contrastlight (or otherwise treated to afford an equivalent efiect) before beingexposed to the image light, the film may be said to be a preexposedfilm. Instead of making the contrast exposure before or after the imageexposure it maybe made simultaneously with the image exposure, as forexam le in projection printing by simultaneous y projecting the imagelight and the contrast light to the film along separate optical paths.Indeed, in printing, either by projection or by contact, oth. lights maypass through the Punting image if the contrast light is absorbed lessthan the other light as would be the case, for example, if the rintingimage is a relief dyed to absorb di erently colored lights in differentdyes and if such differently colored lights are employed for the imageand contrast exposures respectively. In this case the printing image maybe impressed more or less upon the contrast "light as well as upon theimage light. i

If the effect ofthe present invention is impressed upon thephotographicfilm durmg the process of manufacture the film may be exposed in thesame way as ordinary film, except that the exposure may be reduced ashereinafter described. The contrast exposure or pre-exposu're hereinreferred to may be effected in ways other than by exposure to light asfor example by exposure to the fumes 'of a chemical which produces asimilar effect upon hotographic emulsions as is, well-known, or y heat,pressure, electricity, etc.

' The intensity of the contrast light depends upon the effect to beproduced but ordinarily it should be an amount approximately, butpreferably somewhat under, the threshold exposure, the thresholdexposure for the *production'of relief ima es being the expofilm whichis light absorptive and making the contrast exposure with light which isabsorbed by the film, therebyto cause the contrast light to affect thefilm most on the entrantside (that is, the side through which the imagelight enters) where the high-light portions of the resulting relief areformed.

In this connection it is to be noted that the two exposures should bemade from the same side of the film, that is, either both from 'the'emulsion side or both from the celluloid side of the film. This can bestbe done by employing monochromatic light of which the film isabsorptive, that is light having only one color or dominant hue to whichthe film is sensitive. An effect similar to that pro-' duced bymonochromatic light can be obtained with polychromatic l1 ht if the filmhas approximately uniform afisorptivity for all the colors employed. Ifwhite light is used in the contrast exposure the film should absorbsubstantially all the spectral range to which it is sensitive Theinvention further consists in proportioning the image light and thecontrast light-to produce the predetermined contrast gradations desired;and, when using colored 1 ight of which the film is absorptive, ofcorrelating the color of the light and the absorptivity of the film tocontrol the contrast gradations.

The invention further consists in a relief image having more gradualthickness gradations (i. e. variations in relief thickness relative tovariation in light intensity throughout corresponding portions of theobject field) in the thinner portions than in the intermediate portions,and in a color relief image having more gradual opticaldensitygradations the high-light portions than in the half-tone portions(relative to variations in light-intensity throughout the correspondinportions of the object field). The effect 0% the invention isrepresented by a characteristic curve asymptotically approaching eitherthe horizontal line of zero density, known as the exposure axis, or aline parallel thereto.

Referring to the accompanying drawing (Fig. 1) RT is a characteristiccurve showing the thickness gradations of'an ordinary relief image, ODis a characteristic curve showing the opticaldensity gradations of thesame image when stained, and RT and OD are similar curves illustratingthe effect of the present invention, it being understood that the curvesof each pair of relief-thickness and optical density curves arecoincident throughout their intermediate and lower portions.

The lower portion of curve OD which is upwardly concave and whichapproaches the line of zero density asymptotically, is known as theunderexposure region, andit is the absence of this region in ordinaryreliefs, as illustrated by the straight lower portion of curve OD,-which characterizes the diificulties agalnst which this invention isdirected.

Fig. 2 illustrates diagrammatically the linear increase in thickness ofthe relief of the developed film with respect to the intensity (orduration) of the exposure to which it is subjected.

Fig. 3 illustrates diagrammatically the thickness of the developedv (orrather incipiently developed) portion of the film by uniform exposure tospecifically absorbed light just short of or approximating the thresholdexposure (line A) and the relief thickness of the film developed by thesubsequent (or previous) exposure to the image light (curve B) and theoptical reducing effect upon higher 'densities efiected upon treatingthe film with dyes or other coloring agents, (curve C) as obtained inaccordance with the procedure of the present invention.-

It should be here noted that notwithstanding the straight-line curve ODmay correspond to acurate physical reproduction of the object field(that is, it makes screen brightness proportional, neglecting colordifferences, to brightness in the object field) it is inferior for manypurposes to the concave curve OD. For example, in produc ing motionpictures, the negative almost never receives adequate exposure to makeuse of only the straight-line portion of the curve, and the contrastsensibility of the dark-adapted eye in a motion picture theater is sucha rapidly varying function of the vbrightness that for accurate ocularor subjective reproduction of the original scene the straight-line curveis inadequate.

Another important disadvantage of the lack of theunder-exposure regionis the difficulty of printing correctly inasmuch as increase or decreasein printing exposure corresponds'to translation to right or leftrespectively in the figure. -With a straightlight, the images on tion ispreferably employed in conjunction with that described and claimed in mycopending application, Serial No. 512,391, filed on even date herewith,I preferably employ a dye which will serve both purposes. Examples ofsuch dyes are naphtol-yellow and quinoline-yellow, or a mixture of thesedyes, for example in equal amounts, as described in said application.The dye may be incorporated by bathing the film but is preferablyincorporated in the emulsion before being coated on the celluloid. Whilethe amount of dye may be much less than'described in said application,the maximum amount which the emulsion will retain in non-crystallineform when employing said mixture, as described in said application, issatisfactory for most purposes.

Film thus dyed is then exposed both with image light and also withcontrast light. In making color positives separate films may be printedrespectively with complemental negatives representing different coloraspects of the object field,'one or both films also which the emulsionis absorptive, preferably to approximately the threshold exposure. Whenusing yellow dyes such as above menbeing exposed with contrast light oftioned the contrast light is preferably violet,

contrast light, and then running both the positive and the negativefilms through the printer to print, with any suitable printing thespaces previously exposed to the contrast light. When employing theinvention disclosed in my aforesaid application the printing lightemployed in making the second exposure is polychromatic, as described insaid application. If, for example, the finished product is to consist ofa reddish-record 'direct-relief positive and a greenish-recorddirect-relief positive secured together back-to-back in registry, thetwo positives v the back (i. e. through the celluloid) both tothecontrast light. and to the image light, the films thus exposed beingdeveloped, hardened, etched and stained 111 any suitare exposed throughable way to roduce colored reliefs. Th9 positives may e secured togetherafter completion but when securing them together back-to-back they arepreferably joined together immediately after printing and before wettingin order to secure'more accurate register of the complemental images.

If, for example, it is desired to give the finished picture a warm tintthe contrast exposure of the reddish-colored positive may be carriedsomewhat beyond the threshold exposure.

The effect of the contrast exposure may be controlled by regulating thedegree of the exposure, that represented by the lower concave portion ofcurve OD being the effect 6 produced by approximately a thresholdexposure. If the' contrast exposure is decreased the upper end of theconcave portion joins the straight portion at a lower point andintersects the base line at an angle instead of being accuratelyasymptotic to it. If'the contrast exposure is increased the concaveportion asymptotically approaches a horizontal line located above thebase line a distance depending upon the amount of exposure in excess ofthe threshold exposure.

The effect on the contrast gradations may be further controlled byregulating the absorptivity of the emulsion, either in degree or withrespect to the color of the contrast light, by regulating thesensitivity of the emulsion to various colors, and by regulating thecolor of the contrast light.

The image light should be reduced as the contrast light is increased,the total light. preferably producing approximately the same tone in theextreme high lights as is ordinarily produced in printing without anycontrast light, thereby to obtain greatest clearness in the extreme highlights.

The increase in speed produced by the contrast exposure is representedin the figure by the'space between curves OD and OD.

In the production of relief pictures the additional exposure hereindescribed does not produce a veil over the picture unless employed inexcess; indeed it has? the opposite eifect as if the negative had a fogor veil which is eliminated in reproducing according to the presentinvention.

An alternative method of making a relief image whose characteristiccurve is upwardly concave at its lower end consists in exposing theemulsion 'with image light, to such extent that detail in the highlights is recorded in the resulting relief. staining the relief with asuitable dye, preferably substantially' to saturation throughout, andsubsequently washing the relief, e. g. with an aqueous solution. I havefound that the dye washes out in different proportions in the thick,intermediate and thinportions of the relief and that a greaterproportion washes out of the portions of intermediate thickness, that isa greater amount 9f dye washes out of the intermediate portions inproportion to the total amount contained in such portions than washesout of the thinner and thicker portions in proportion to the amountscontained therein respectively. Thejemulsion should be absorptive asabove described .but need not be so strongly absor tive. The dye washesout more or less rapidly depending upon the alkalinity or acidity-of thewash solution, the rate being increased by increased alkalinity anddecreased by increasedacidity in c'aseof acid dyes. The effect of thewash may therefore be controlled by varying the acidity or alkalinity ofthe solutlon; also by regulating the time of washing and the degree ofagitation of the solution. This alternative method is more diflicult topractice than the method involving a contrast exposure and does not ivesuch good results, particularly as regar s uniformity of color balancebetween the complemental images. However,- for' certain purposes aslight wash may be employed to advantage' to supplement the contrastexposure method.

While the present invention is particularly applicable to reliefprocesses it is obv1- ously applicable wherever it is desirable to alterthe characteristic curve, particularly by bending the lower portion 0the curve.

Iclaim: I

1. The method f producing a photo-- a hic printing m trix comprisingprinti ii g ii film With light distributed to produce a latent imagetherein, altering the contrast gradations of the image by exposing thefilm with correspondingly distributed light, and converting the alteredlatent image into a photographic printing matrix.

2. The method of producing a colo'rpicture which comprises printing animage on a sensitized film followed by uniformly exposingthe film fromthe same side, deyelopmg and selectively coloring the film in accordancewith the double exposure.

Ill

The method of producing photographic pictures comprising exposinga filmwith light distributed substantially uniformly and also with lightdistributed to produce an image therein, the two lights beingproportioned to produce predetermined contrast gradations in the image.

4. The method of producing relief pic-- tures which comprises exposing afilm with light distributed substantially uniformly and simultaneouslyalso with light distributed to form an image. therein, the two lightsbeing proportioned separately to make substantially no image in thehigh-light portions but conjointly to record an image in such portions.

5. The method ofproducing relief images comprising printing a film withlight distributed to produce a latent image therein,

altering the contrast gradations of the image by exposing the film withdiiferently dis tributed light, and converting the altered image intoarelief.

6. The method of producing relief images comprising exposing a filmsubstantially uniformly and also non-uniformly to form an image therein,the two exposures being correlated to produce a predetermined detail inthe high-lights, and subsequently converting the image into a relief.

7. The method of producing a photographic printing matrix comprisingexposing a film substantially uniformly and also non-uniformly to forman image therein,

the two exposures being correlated to pro-- duce a predetermined detailin the highlights, and subsequently converting the image into aphotographic printing matrix.

8. The method of producing photographic pictures comprising exposing afilm which is absorptive of light of a certain color with lightdistributed toproduce a picture and also with light of said color toalter the contrast gradations of the picture in a predetermined manner.

9. The method of producing relief pictures which comprises exposing afilm, at some stage before development, in addition to the imageexposure, an amount suflicient to carry the image exposure, in thehighlight regions, beyond the threshold exposure and subsequentlyremoving the residual undeveloped portions of the film for theproduction of relief pictures.

- 10. The method of producing photographic pictures comprising exposinga film with colored light and also with light distributed to produce animage therein, the two lights being proportioned to producepredetermined contrast gradations in the image. I

11. The method of producing photographic pictures comprising exposing afilm with colored light of which the film is largely absorptive and alsowith light distributed to produce an image therein, the two lights being proportioned to produce predetermined contrast gradations in theim'age.

12. The method of producing photographic pictures comprising exposing a.film with substantially monochromatic light and also with lightdistributed to produce an image therein, the two'lights beingproportioned to produce predetermined contrast gradations in the image.

13. The method of producing photographic pictures comprising exposing afilm with colored light distributed substantially uniformly and alsowith light distributed to produce an image therein, the two lights beingproportioned to produce predetermined contrast gradations in the image.

14. The method of producing photographic pictures comprising exposingafilm with colored light of which the film is largely absorptivedistributed substantially uni-- ing proportioned to producepredetermined contrast gradations in the image.

15. The method of producing photographic picturescomprising exposing afilm with substantially monochromatic light distributed substantiallyuniformly and also with light distributed to produce an image therein,the two lights being proportioned to produce predetermined contrastgradations in the image.

16. The method of producing photographic relief images comprisingexposing a film, which is rapidly absorptive of light of a certaincolor, with substantially monochromatic light of approximately saidcolor, also exposing the film with light distributed to form an imagetherein, the two lights being relatively proportioned to produce apredetermined degree of contrast in the high-lights, and subsequentlyconverting the image into a relief.

17. The method of producing photographic pictures which comprisesexposing a film, at some stage before development, in addition to theimage exposure with light of which the film is absorptive, andregulating the degree of ,absorption to control the contrast graduations18. The method of producing photographic pictures which comprisesexposing a film. at some stage before development, in addition to theimage exposure, with colored lights of which the film isabsorptive, andcorrelating the color of the light and the absorptivity of the film tocontrol the contrast gradations.

19. The method of altering the contrast graduations of a photographicpicture which comprises exposing a film with light of which the film isstrongly absorptive to produce a predetermined increase in the'concavityof the lower portion of the characteristic curve of the picture.

20. The method of producing a photographic picture 'which comprisesexposing a film to form a latent image representing a characteristiccolor aspect of the object field and altering the contrast gradations ofthe picltlure by exposing the film with secondary 21. The method ofproducing a photographic picture which comprises exposing a film to forma latent image representing a characteristic color aspect of the objectfield and altering the contrast gradations of the picture by exposingthe film with light of which the film is strongly absorptive.

22. The method of producing a photographic picture which comprisesexposing a film with image light and with contrast light whose spectralrange is correlated with the absorptivity of the film to producepredetermined contrast gradations.

23. In the production of photographic pictures by a process whichtends-to produce pictures 'h'aving contrast gradations repre-' sented bya characteristic curve whose lower portion tends toward straightness,the method which comprises rendering said portion of the vcharacteristic curve approximately asymptotic to the exposure axis bygradual optical-density gra ations m the high-light portions than in thehalf-tone portions.

26. A printing matrix image having optical-density gradationsrepresented by a characteristic curve in which the lower portion islocated above a tangent to the central portion of the curve.

27. A printing matrix image having more gradual optical-densitygradations 1n the high-light and low-light portions than in thehalf-tone portions.

28. A printlng matrix image in which the gradations of optical-densityare greater in the intermediate portions of the image than in thelighter portions, for the same range of light intensities in the scene.

29. A printing matrix image in which the gradations of optical-densityare greater in the intermediate portions of the image than in thelighter portions, for the same range of light intensities in the scene,and which is substantially free from'halation effects.

30. A photographic printing matrix having selective dye absorptioncharacteristics represented. by a characteristic curve in which thelower portion is concave.

31. A photographic printing matrix having selective dye absorptioncharacteristics represented by a characteristic curve in which the lowerportion approaches asymptotically to a line parallel to the exposureaxis. a

32. A photographic printing matrix having more gradual dye absorptiongradations in the high-light portions than in the halftone portions.

33. A photographic printing matrix comprising a stratum whosedyeabsorption capacity varies in accordance with light values of thescene depicted and a thin stratus of uniform absorptivity.

34. A photographic rintingmatrix in which the gradations o dyeabsorption are hotob 36. Photographic film for use in the pro- Iductionof relief images comprising an emul-' sion which has been'pre-exposed from the the threshold exposure.

37. Photographic film for use in the production of relief imagescomprising an emulsion which has been pre-exposed from the back anamount approximating the threshold exposure for the production of arelief.

38. Photographic film for use in the production of relief imagescomprising an emulack an amount hot substantially exceedingsion whichhas'been pre-exposed to a limited depth on its support side. 7

39. Photographic film for use in the production of relief imagescomprising an emulsion which has been pre-exposed to a limited depth onits support side an amount not substantially exceeding thethresholdexposure.

40. Photographic film for use in the production of relief imagescomprising an emulsion which has been pre-exposed to a limited depth onits support side an amount approximating the threshold exposure for theproduction of a relief.

41. A photographic film having super-' posed complemental relief imageswhose thickness gradations are represented by a characteristic curve inwhich the'lower por-' tion is concave.

42. A photographic film having superposed complementaldirect-reliefimages whose thickness gradations are represented by a characteristiccurve in which the lower portion approaches asymptotically to a lineparallel to the optical axis.

43. A photographic film comprisin an integral'film having on. oppositesides t ere-.

portions than in the thicker portions.

44. A relief' positive having thickness gradations represented by acharacteristic curve in which the lower portion is concave.

45. A relief positive having thickness gradations represented by acharacteristic curve in which the lower portion a proachesasymptotically to a line parallel o the exposure axis. 1 i

' 46. A relief positive having thickness gradations represented by acharacteristic curvein which the lower portion approaches asymptoticallyto the lineof zero density. I 47. A relief image having more gradualthickness gradations in-the thinner portions than in the intermediateportions.

teristic curve 1n which the lower portion is located above a tangent tothe central por-' tion of the curve.

50. A color relief image having more gradual optical-density gradationsin the high-light portions than in the half-tone portions. I

51. A color relief image in "which the gradations of optical-density aregreater in the intermediate portions of the image than in the thinnerportions, for the same range of light intensities in the scene.

52. A color relief image in which the gradations of optical-density aregreater in the intermediate portions of the image than in the thinnerportions, for the same range of light intensities in the scene, andwhich is substantially free from halation effects.

53. A" relief picture comprising this 29th a. stratumwhose thicknessvaries in accordance with light values of the scene depicted and a.-thin stratum of uniform thickness.

. 54. A color picture comprising a su port j carrying an inner coloredstratum o umform thickness and an outer similarly colored stratum 'whosethickness varies in accordance with the light values of onecharacteristic hue of the scene depicted, the two strata togetheryielding the desired contrast gradations throughout the high-light andhalf-tone portions.

55. A colorpicture comprising a stratum in which the color distributionvaries in accordance with the light values of one characteristic hue ofthe scene depicted and ana picture having,

other stratum in which the color is relatively uniformly distributed. v

56. A stained picture comprising a stra tum in which the dyedistribution varies in accordance with light distribution in the scenedepicted and another stratum in which the dye is relatively uniformlydistributed.

Signed by me at Boston, Massachusetts day of October 1921.

' EASTMAN A. WEAVER."

